The process of preparing fermented malt beverages, such as beer, ale, porter, malt liquor and other similar fermented alcoholic brewery beverages, hereinafter referred to simply as "beer" for convenience, is historically well-established. As practised in modern breweries, the process, in brief, comprises preparing a "mash" of malt, usually with cereal adjuncts, and heating the mash to solubilize the proteins and convert the starch into sugar and dextrins. The insoluble grains are filtered off and washed with hot water which is combined with the soluble material and the resulting wort boiled in a brew kettle to inactivate enzymes, sterilize the wort, extract desired hop components from added hops, and coagulate certain protein-like substances. The wort is then strained to remove spent hops and coagulate, then cooled and pitched with yeast and fermented. The fermented brew known as "green" or "ruh" beer is then aged ("lagered") and clarified, filtered, and carbonated to produce the desired beer. In the widely practiced high gravity brewing procedure, beer is brewed at a slightly elevated alcohol content of say 7% to 8% vol/vol alcohol content and this is then diluted to the desired value of say 5% vol/vol.
As is well known, such beers generally develop a haze upon elapse of time and/or through changes in temperature of the beer. This haze is considered to be made up of two types:
(a) "chill haze" which is temperature sensitive and may disappear as the temperature of the beer is raised to, say, room temperature; and PA1 (b) "permanent haze" which, as the name implies, once created remains.
If the beer is consumed warm, as in some European countries, then chill haze may be less of a problem but where beer is consumed cold, as is customary in North America, chill haze can be a serious problem.
In any event, in modern times for various reasons such as the closing of many local breweries, etc., the time from when the beer is stored, whether it is in tanks, kegs, bottles, cans, etc., to when it is consumed by the public has increased and this results in the amount of haze which will be formed increasing and, although as indicated above, some of the haze will be of the temperature sensitive-type, the precipitated amount of the components responsible for the permanent haze increases and, eventually, the total haze becomes visible at room temperature.
The exact nature and mode of formation of haze in beer is not known but it is generally accepted that haze comprises significant amounts of proteins, yeast cells, metals, cell components, polyphenols and various other materials.
The problem of haze formation has been addressed in many ways. The traditional way is, of course, to subject the beverage to a lagering step in which the beverage is stored at near zero temperatures for periods of time ranging from weeks to, in extreme cases, up to several months during which time the yeast cells and proteins settle out and, additionally, the taste of the beer may improve. However, that step alone is not adequate for modern needs especially in view of the time required which is responsible for a significant fraction of the overall costs, and hence, significant effort continues to be expanded to eliminate or at least reduce this problem. For example, use of polyvinylpyrrolidone (PVP) to stabilize beer by combining with the polyphenols well documented, refer to U.S. Pat. Nos. 2,688,550; 2,939,791 and others. U.S. Pat. No. 3,251,693 teaches adding various silicates particularly calcium magnesium or zinc silicates to the beer (or wort) and U.S. Pat. No. 3,940,498 teaches the use of certain acid treated synthetic magnesium silicates. For example U.S. Pat. No. 3,940,498 teaches adding an acid-treated synthetic magnesium silicate to the beer. However, although these methods do alleviate the problem, they by no means eliminate it and are becoming less favored as the addition of any additives or processing aids to all foods is becoming less desirable.
It has also been proposed, in Australian Patent Specification 224576 to convert beer to a slush ice condition which is maintained for up to seventy-two hours and subsequently melting the beer and immediately separating out the precipitated material. If the beer contains material which can re-dissolve before it can be removed by filtration or centrifugation, then a general absorbent material such as bentonite (or asbestos) is added prior to freezing the beer to ensure that the precipitated material is definitely converted into and maintained in an insoluble form before it can re-dissolve upon melting. Beer has been subjected to freezing in other processes, specifically processes involving the production of beer concentrates. For example, Canadian Patent No. 673,672 involves freezing beer to produce a slurry of concentrated beer, ice and other solids including yeast cells, removing the ice and other solids from the desired concentrated beer, which has concentrated up to five-fold relative to the starting beer. The ice is discarded or passed into a system to recover beer or desirable components thereof that are entrained on the ice. All freeze concentration processes suffer from the fact that the ice removed can carry away excessive amounts of the desired material and recovery of that material which is occluded or retained on the ice, by washing extraction or other means, brings its own problems--refer for example to Canadian Patent No. 710,662. Also, the practical process is usually multistage with successive stages being effected at temperatures reduced relative to earlier stages, this being quite common in the freeze concentration art--refer for example to Canadian Patents No. 601,487 and No. 786,308. This latter patent has the same inventor and proprietor as Canadian Patent No. 673,672 and covers products produced by the latter patent. Despite the quite amazing claims made for the products produced under this patent, it does not seem to have ever been commercially exploited. U.S. Pat. No. 4,885,184 teaches a process for preparing flavored malt liquors wherein an aged fermented wort is freeze concentrated generally to the 20% to 30% alcohol by volume level, and various flavourings then added. In the freeze concentration process described in Canadian Patent No. 872,210 it is the wort which is freeze concentrated, this apparently providing efficiencies in obtaining a higher yield or extract from the brew materials than is obtained in a regular brew.
As indicated above, the development of haze in beer is, obviously, still a significant practical problem despite the extensive efforts made in the past, and still being made, to solve it.
An object of the present invention is to provide a process for continuously processing beer at low temperatures.